Enthalpy based mathematical modelling for thermal energy storage filled with paraffin encapsulated balls as storage material

Abstract

Numerical modeling of latent heat thermal storage (LHTS) is always complex to solve because of the necessity to tediously track the moving boundary, which happens due to the continuous variation of solid–liquid interface, during the melting or freezing process of phase change materials (PCM). Moreover, when commercial grades of paraffin are employed as Phase change storage materials for thermal energy storage applications, the phase transition will not happen at a particular fixed temperature but in a narrow range. Also, such paraffin exhibits several zones of transitions such as solid–solid and solid–liquid. The enthalpy (or fixed domain) method is one of the convenient methods to model problems involving phase change (or phase change materials) with the above mentioned conditions. In this paper, the mathematical modeling by enthalpy method for a LHTS system filled with ball shaped PCM containers as storage materials and its numerical solution procedures were discussed. The numerical procedure that considers the solid to solid transition of PCM and enthalpy-temperature relationships for PCMs that exhibit unsymmetrical transition zones before and after the peak transition temperature during the solid–solid and solid–liquid transitions were introduced and analysed.